Could not find class 'com.esri.android.map.MapView', referenced from method com.esri.arcgis.android.samples.helloworld.HelloWorldActivity.onCreate

Does there have to be a layout named `MapView`? If so,I do not have in my project. Could you please tell me how can I get it into the project?

I also have all source folders in the project. Even mapview, don't know why it's showing this kind of error. I need help with this project and I need to complete it within a few days,but I;m stuck due to this error and can't proceed.I'm facing this same problem in all my projects, even though every one of them I tried is a sample provided by ArcGIS. I'd appreciate help asap,Please. Thanks